Inflators and method for manufacturing inflators

ABSTRACT

A closure assembly for an inflator comprises a housing and an outlet plate disposed within the housing. The outlet plate has an outlet opening configured to receive a burst disk. The outlet plate is joined to the housing by a deformation resistance weld. The deformation resistance weld is formed by contacting the outlet plate with a first electrode, contacting an exterior portion of the housing with a second electrode, and applying a voltage through the first and second electrodes to adhere a portion of the housing to a portion of the outlet plate.

BACKGROUND

The present invention relates to pressurized containers, and morespecifically, to airbag cushion inflators and to apparatuses and methodsfor manufacturing the same.

It is known to provide an inflatable restraint system including aninflator and inflatable airbag cushion for protecting the occupants of atransportation vehicle during collisions. Automotive vehicles, forexample, can be supplied with driver side airbag modules, passenger sideairbag modules, and side airbag modules. Such airbag assemblies, forexample, may be located within the hub of the steering wheel and in arecess in the instrument panel for protection of the vehicle occupantsseated in opposing relation to such assemblies. In other examples, suchairbag assemblies may be located within the seats and/or door panels forprotection of the occupants during a side-impact event.

Methods for manufacturing airbag inflators typically require the weldingof a number of parts together, particularly in light of the increasingcomplexity of inflators. Prior welding techniques used to manufactureairbag inflators have been either laser welding or friction welding.

Laser welding is a welding technique used to join multiple pieces ofmetal through the use of a laser. The beam provides a concentrated heatsource, allowing for narrow, deep welds and high welding rates. Theprocess is frequently used in high volume applications, such as in theautomotive industry. Some of the shortcomings of laser welding are thevery high cost of equipment and consumables such as shielding gas andlenses, high cycle time, uncertainty of consistently making a leak-tightjoint, and somewhat low weld strength with a potential for porosity (dueto high cooling rates, cracking can be a concern, especially whenwelding high-carbon steels).

Friction welding is a technique used to weld thermoplastics or metals bythe heat generated through mechanical friction by rubbing the members tobe joined against each other under pressure, with the addition of anupsetting force to plastically displace material. Some of theshortcomings of friction welding are the high cost of equipment, weldflash on both sides of the weld joint (some of which may be loose anddifficult to remove), difficulty in controlling the finished part lengthupon welding, high cycle time, and the difficulty of gripping thinplates using a friction welding apparatus.

Accordingly, it is desirable to provide for the manufacturing of airbaginflators using welding techniques that can overcome at least some ofthe shortcomings of the prior welding techniques.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention relate to a closureassembly for an inflator. The closure assembly comprises a housing andan outlet plate disposed within the housing. The outlet plate has anoutlet opening configured to receive a burst disk. The outlet plate isjoined to the housing by a deformation resistance weld. The deformationresistance weld is formed by contacting the outlet plate with a firstelectrode, contacting an exterior portion of the housing with a secondelectrode, and applying a voltage through the first and secondelectrodes to adhere a portion of the housing to a portion of the outletplate.

Exemplary embodiments of the present invention also relate to aninflator for inflating an inflatable cushion of an airbag module. Theinflator comprises an outer housing and a divider plate secured withinthe outer housing to define a first chamber and a second chamber of theouter housing. The divider plate has an orifice disposed therein. Theorifice provides fluid communication between the first chamber and thesecond chamber. The divider plate is joined to the outer housing by adeformation resistance weld. The deformation resistance weld is formedby contacting the outer housing with a first electrode at an exteriorportion of the outer housing proximate to the divider plate, contactingthe divider plate with a second electrode disposed within the outerhousing, and applying a voltage through the first and second electrodesto adhere a portion of the outer housing to a portion of the dividerplate.

Exemplary embodiments of the present invention also relate to aninflator for inflating an inflatable cushion of an airbag module. Theinflator comprises an inflator housing and a base plate configured toengage with an assembly for mounting the inflatable cushion to theairbag module. The base plate is joined to an open end of the inflatorhousing by a deformation resistance weld. The deformation resistanceweld is formed by contacting the base plate with a first electrode,contacting an exterior portion the inflator housing with a secondelectrode proximate to the base plate, and applying a voltage throughthe first and second electrodes to adhere a portion of the inflatorhousing to a portion of the base plate.

Exemplary embodiments of the present invention also relate to a methodfor securing an outlet plate within a housing of an inflator. The methodcomprises inserting the outlet plate into the housing. The methodfurther comprises applying pressure against the outlet plate with afirst electrode in a first direction. The method further comprisesapplying pressure against an exterior portion of the housing with asecond electrode in a second direction. The method further compriseswelding the outlet plate to the housing by applying a voltage throughthe first and second electrodes to adhere a joining portion of theoutlet plate to a joining portion of the housing.

Exemplary embodiments of the present invention also relate to a methodfor securing a divider plate within an outer housing of an inflator. Themethod comprises inserting the divider plate within the outer housing.The method further comprises inserting a first electrode configured toengage a portion of the divider plate into the outer housing. The methodfurther comprises applying pressure against the divider plate with thefirst electrode electrode in a first direction. The method furthercomprises applying pressure against an exterior portion of the outerhousing proximate to the divider plate with a second electrode in asecond direction. The method further comprises welding the divider plateto the outer housing by applying a voltage through the first and secondelectrodes to adhere a joining portion of the divider plate to a joiningportion of the outer housing.

Exemplary embodiments of the present invention also relate to a methodfor securing a base plate to an inflator housing of an inflator. Themethod comprises disposing the base plate proximate to an open end ofthe inflator housing. The method further comprises applying pressureagainst an exterior portion of the inflator housing proximate to thebase plate with a first electrode in a first direction. The methodfurther comprises applying pressure against the base plate with a secondelectrode in a second direction. The method further comprises weldingthe base plate to the inflator housing by applying a voltage through thefirst and second electrodes to adhere a joining portion of the baseplate to a joining portion of the inflator housing.

Exemplary embodiments of the present invention also relate to a weldingapparatus for deformation resistance welding a divider plate within anouter housing of an inflation device. The apparatus comprises a firstelectrode and a second electrode. The first electrode is configured tobe inserted into the outer housing. The first electrode has a contactend with an opening configured to receive a centrally protruding portionof the divider plate therein. The first electrode has an outer peripherythat is smaller than an inner dimension of the housing. The secondelectrode comprises a pair of members removably secured to each other.The pair of members define an inner opening. The pair of members areconfigured to apply pressure to an exterior surface of the outer housingwhen the pair of members are secured to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an inflatable cushion in a storedposition;

FIG. 2 is a side elevational view of an inflatable cushion in a deployedstate;

FIG. 3 is a cross-sectional view of an inflator constructed inaccordance with an exemplary embodiment of the present invention

FIG. 4 is a cross-sectional view of an exemplary apparatus after forminga deformation resistance weld between a closure housing and an outletplate of a closure assembly in accordance with an exemplary embodimentof the present invention;

FIG. 5 is a partial cross-sectional view of the closure housing and theoutlet plate of FIG. 4 before the exemplary deformation resistance weldis formed;

FIG. 6 is a partial cross-sectional view of the closure housing and theoutlet plate of FIG. 4 after the exemplary deformation resistance weldis formed;

FIG. 7 is a cross-sectional view of an exemplary apparatus prior toforming a deformation resistance weld between an outer housing and adivider plate of an inflator in accordance with an exemplary embodimentof the present invention;

FIG. 8 is a partial cross-sectional view of the exemplary apparatus ofFIG. 7 after forming the deformation resistance weld between the outerhousing and the divider plate of the inflator in accordance with anexemplary embodiment of the present invention;

FIG. 9 is a partial cross-sectional view of the outer housing and thedivider plate of FIGS. 7 and 8 after the exemplary deformationresistance weld is formed;

FIG. 10 is a partial cross-sectional view of the outer housing and thedivider plate of FIGS. 7 and 8 after an alternative exemplarydeformation resistance weld is formed;

FIG. 11 is a cross-sectional view of an inflator constructed inaccordance with an alternative exemplary embodiment of the presentinvention;

FIG. 12 is a view of the interior of an automotive vehicle incorporatingexemplary driver side and passenger side air bag modules;

FIG. 13 is an exploded perspective view of an exemplary driver sideairbag module;

FIG. 14 is a partial cross-sectional view of an exemplary apparatusprior to forming a deformation resistance weld between an inflatorhousing and a base plate of an inflator assembly in accordance with anexemplary embodiment of the present invention;

FIG. 15 is a cross-sectional view of the exemplary apparatus of FIG. 14after forming the deformation resistance weld between the inflatorhousing and the base plate of the inflator assembly in accordance withan exemplary embodiment of the present invention; and

FIG. 16 is a partial cross-sectional view of an exemplary apparatusprior to forming a deformation resistance weld between an inflatorhousing and a base plate of an inflator assembly in accordance with analternative exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention are directed to devicesfor the containment and release of pressurized gas from an airbaginflator, and to apparatuses and methods for manufacturing the same.Particularly, as will be disclosed herein, exemplary embodiments of thepresent invention are directed to methods of manufacturing inflatorsusing processes that involve the welding of certain parts to each otherusing deformation resistance welding techniques (DRW), and to inflatorsthat have been manufactured using these techniques.

DRW is a resistance welding method that has been developed to join metaltubes to solids, sheet metal and other tubes. The process atomicallybonds metals and creates solid-state joints through the heating anddeformation of the mating surfaces. DRW can be used to form nearinstantaneous, full strength, leak-tight welds by heating metal surfacesonly to the point of softening, followed by rapid, engineeredcompression of the joint. Slight interference at joint locationfacilitates deformation during weld process, but is not essential. Theprocess bonds metals and creates solid-state joints without requiringfiller welding material through the heating and deformation of matingsurfaces. DRW allows the joining of not only similar, but alsodissimilar materials (specifically metals), providing designers with theability to create lean structural assemblies by using tubularcomponents. For example, contoured sheet metals can be welded to tubes.

DRW thus provides for more control over dimensions (in particular, DRWcan be utilized to obtain a predictable post-weld member length) and canbe used to create leak-tight joints that are capable of holding fluidsor gases under pressure and heat. These joints can have strengthexceeding that of the parent metals. The DRW process can reduce thecycle time (which is independent of joint size in DRW) and the cost ittakes to make a variety of structures that involve hollow members suchas airbag inflators, as will be described herein. The improvedresistance welding method increases design flexibility and efficiencywhile helping to cut cost, investment, and part weight. Examples ofdeformation welding techniques are described in detail in U.S. patentapplication Ser. No. 10/253,099, published as Pub. No. 2004/0056001 onMar. 25, 2004, U.S. patent application Ser. No. 10/914,837, published asPub. No. 2005/0006352 on Jan. 13, 2005, and U.S. patent application Ser.No. 11/370,427, published as Pub. No. 2006/0231597 on Oct. 19, 2006, thedisclosures of which are incorporated herein by reference.

Referring now to FIG. 1, a non-limiting exemplary embodiment of a sideairbag or inflatable cushion 10 mounted to a vehicle 12 in a stored ornon-deployed state is illustrated. In exemplary embodiments, side airbagmodules can comprise inflatable cushions or curtains that traverse aside portion of the vehicle when they are deployed in accordance with apredetermined activation event. Generally, such a device is locatedalong a side of the vehicle in an uninflated state and, upon activation,deploys an inflatable curtain along a side portion of the vehicle. Sideimpact airbags or inflatable cushions are often mounted in closeproximity to the vehicle's roof rail, doorframe, center pillars, or, insome instances, within the side door. Accordingly, the space or housingfor the uninflated airbag is typically compact and extends or traversesalong the window area or frame.

In the exemplary embodiment illustrated in FIG. 1, vehicle 12 comprisesa front pillar 14, a rear pillar 16, and, if the vehicle is so equipped(for example, it has more than one door per side), a center pillar orpillars 18. Such pillars are commonly referred to as A, B, C and Dpillars. Inflatable cushion 10 is stored and mounted on or proximate toa vehicle roof rail 20 beneath a headliner.

As illustrated, the rear portion of inflatable cushion 10 is in fluidcommunication with a gas generator or inflator 30 positioned to providean inflation gas to inflate inflatable cushion 10 via a diffuser tube 31having a plurality of diffuser openings disclosed therein. It should, ofcourse, be understood that as applications may vary, the inflator may bepositioned in other locations than those illustrated in the presentexemplary embodiment. For example, the inflator may be located in aposition farther forward in the vehicle such as the door pillar, thefront pillar, or another location or locations. In addition, diffusertube 31 may be configured to extend through a portion of the inflatablecushion, wherein a plurality of openings is positioned in the diffusertube that traverses through an interior portion of the inflatablecushion. Thus, the presented location is provided as an example and thepresent invention is not intended to be limited by the same. In analternative exemplary embodiment, the inflator may be remotely locatedand a conduit or other fluid providing means used to supply theinflating gas from the inflator to the inflatable cushion.

In exemplary embodiments, inflatable cushion 10 may be comprised of anyairbag material suitable for holding gas. For example, the inflatablecushion can comprise two sheets of woven nylon fabric lined withurethane or other substantially impervious material such as silicone.The two urethane coated nylon sheets in this exemplary embodiment aresecured to one another along an outer periphery thereof to define theoverall airbag shape. Prior to deployment, the inflatable cushion isstored in a compartment mounted to roof rail 20 or proximate to the roofrail as shown in FIG. 1. To store inflatable cushion 10 in thecompartment, the uninflated cushion is folded into a configuration thatallows it to occupy a small discrete area within the vehicle interior.

FIG. 2 illustrates an exemplary embodiment of inflatable cushion 10 inan inflated or deployed state. As illustrated in FIG. 2, inflatablecushion 10 comprises a deploying edge 22, which comprises the bottomportion of the inflatable cushion that traverses across the windowopenings or window frames of the vehicle. Inflatable cushion 10 alsocomprises a forward edge 24, a rearward edge 26 and a fixed edge 28.Fixed edge 28 represents the portion of inflatable cushion 10 thatremains in substantially the same position regardless of whether theinflatable cushion is deployed or not.

Many different types of airbags or inflatable cushion arrangements (forexample, internal cavities, tethers, and/or seams) can be used withexemplary embodiments of the present invention. Therefore, it should beunderstood that the configuration of inflatable cushion 10 may vary andthat the illustrations in FIGS. 1 and 2 are provided as non-limitingexemplary embodiments. The present invention is not intended to belimited to the specific configurations provided herein in the exemplaryembodiments, as they are considered ancillary to the present invention.

Referring now to FIG. 3, an exemplary embodiment of a side airbaginflator 30 is illustrated. Inflator 30 comprises a longitudinallyextending, generally annular inflation housing 34, a divider plate 80,an initiator 36, and an external closure assembly 78. Divider plate 80is secured within inflation housing 34 to define and partition a firstinflation chamber 32 and a second inflation chamber 76 within theinflation housing 34.

Closure assembly 78 of the present exemplary embodiment includes alongitudinally extending, generally annular closure housing 38, anannular outlet plate 40 that is joined to the closure housing 38 andsecured to inflation housing 34 at one end of first inflation chamber32, and a burst disk 44. Outlet plate 40 defines an outlet opening 42that is sealed by a burst disk 44 that can comprise a thin metalmembrane in exemplary embodiments. As illustrated in FIG. 3, initiator36 is mounted within closure assembly 78.

In the present exemplary embodiment, closure housing 38 is joined tooutlet plate 40 using DRW techniques, as illustrated in FIG. 4, to forma deformation resistance weld joint 41. Closure housing 38 is generallyannular and has an inside and an outside surface 46, 47. Closure housing38 also includes an upper end flange 50 longitudinally extending fromoutside surface 47 of the housing toward outlet plate 40.

Outlet plate 40, as shown in FIG. 4, is formed with a burst disk flange52 that extends radially inwardly in a direction generally transverse tothe annular wall of closure housing 38. Burst disk flange 52 isconfigured to engage burst disk 44 so that the burst disk will extendgenerally transversely to closure housing 38 within the annulus ofoutlet plate 40. Outlet plate 40 is also formed with a lower end flange54 extending longitudinally from burst disk flange 52 in a directiongenerally opposed to upper end flange 50 of closure housing 38. Lowerend flange 54 is offset radially inwardly in a direction generallytransverse to upper end flange 50 of closure housing 38 to define arecess 56 below the outside portion of outlet plate 40.

Inside surface 46 and upper end flange 50 of closure housing 38 and thewall of outlet plate 40 adjacent to recess 56 respectively define therespective joining (that is, mating or joining) surfaces of weld joint41 between the closure housing and the outlet plate. During the weldingprocess, which is sequentially illustrated in FIGS. 5 and 6, outsidesurface 47 of closure housing 38 is longitudinally aligned with theoutside surface of outlet plate 40. As best seen in FIG. 5, however, thetransverse width of the annular wall of closure housing 38 is greaterthan the transverse width of recess 56 of outlet plate 40 at the outsetof the welding process. This differential provides for diametricalinterference in the mating parts to permit deformation and sliding ofthe mating surfaces along each other during the weld process. In thepresent exemplary embodiment, the upper end of inside surface 46 ofclosure housing 38 is provided with an angled chamfer 51 for engaginglower end flange 54 of outlet plate 40 to prevent shorting duringinitiation of the welding process. In the present exemplary embodiment,angled chamfer 51 is provided with a relatively sharp corner 55 toprovide for high current density at the initiation of the weldingprocess.

With upper end flange 50 inserted into recess 56 and angled chamfer 51contacting lower end flange 54 of outlet plate 40, as described aboveand shown in FIG. 5, weld joint 41 can then be formed between closurehousing 38 and the outlet plate 40. During the welding process, a testplate may be provided to extend transversely within the annulus ofoutlet plate 40 and simulate the positioning of burst disk 44 in thecompleted inflator assembly. The test plate may be configured to have aninterstitial region to simulate the electrode footprint in burst disk44.

In the present exemplary embodiment, weld joint 41 is formed by slidinginside surface 46 of closure housing 38 along lower end flange 54 ofoutlet plate 40 while forcing the two components against each otherunder sufficient pressure to form an interference fit. As shown in FIG.6, the welding process is complete at a point at which upper end flange50 engages outlet plate 40. In this position, as shown in FIG. 6, thespace between upper end flange 50 and lower end flange 54 forms anexpulsion or flash trap 53, which is designed to improve the quality orthe cleanliness of weld joint 41 by preventing weld flash from reachingthe inner diameter of the functioning area of weld joint 41.

To perform the welding process described above, inside surface 46 ofclosure housing 38 is compressed against lower end flange 54 of outletplate 40 by engaging the housing with a first electrode 48, and applyingpressure against the housing 38 with the first electrode 48 in a firstdirection generally perpendicular to the annular wall of the housing 38,while simultaneously engaging the outlet plate 40 with a secondelectrode 58, and applying pressure against the outlet plate 40 with thesecond electrode 58 in a direction perpendicular the first direction.The interference fit is formed by applying sufficient pressure throughfirst and second electrodes 48, 58 and moving at least one of theelectrodes toward the other electrode, while resistance welding togetherinside surface 46 of closure housing 38 and lower end flange 54 ofoutlet plate 40, by applying an electrical current between theelectrodes for resistance heating the housing 38 and the outlet plate 40to a temperature at which a metallurgical bond is formed between thejoining surfaces. Pressure and electrical current can be maintained at alevel and for a period of time sufficient to substantially softenclosure housing 38 and outlet plate 40 and allow a portion the softenedmaterial of the housing to flow into the interference juncture and weldthe two parts together. In this manner, the softened material can beforced to flow through a relatively lengthy juncture, and the componentsto be joined can be maintained at an optimum temperature for ensuringthat a complete and high quality weld is formed.

Further, in exemplary embodiments, it may be advantageous apply pressureand a first level of electrical current flow through closure housing 38and outlet plate 40 for a first period of time, for softening thehousing by electrical resistance heating and causing the softenedhousing 38 to deform against the outlet plate 40, under the pressureexerted by first and second electrodes 48, 58, followed by theapplication of a second level of electrical current, higher than thefirst level of current, for a second period of time sufficient to atleast partially melt the housing, and form deformation resistance weldjoint 41 between the housing 38 and the outlet plate 40.

It should be appreciated that for a joint of this type, the ability toslide inside surface 46 of closure housing 38 along lower end flange 54of outlet plate 40 using DRW techniques eliminates the close tolerancemachining required in prior joining methods, simplifies the form withwhich recess 56 can be provided, and considerably simplifies,facilitates, and decreases the cost of both construction and operationof the equipment used to make the joint. For instance, in the exemplaryembodiment described, the point at which upper end flange 50 contactsoutlet plate 40 controls the length of weld joint 41. Alternatively,stops for first and second electrodes 48, 58 may be precisely designedfor even more precise control of the finished part length to make theperformance of the inflator more repeatable. For instance, in exemplaryembodiments, the transverse width of the annular wall of closure housing38 and the length of weld joint 41 can be substantially equivalent toprovide for increased weld strength. In addition, the use of DRWtechniques can provide for a reduced cycle time, much improved weldstrength and durability, and a decreased the heat effect in the parentmetals caused by weld heat by providing the ability to heat treat thecomponents in the weld strength.

Referring again to FIG. 3, after closure housing 38 and outlet plate 40have been welded together as described above, a wedge support member 60and a movable wedge member 62 are disposed between burst disk 44 andinitiator 36. Support member 60 surrounds a portion of initiator 36. Inaccordance with the present exemplary embodiment, wedge member 62 iswedged between burst disk 44 and support member 60. In addition, aprojectile or pin 64 is received in an opening 66 of support member 60.Pin 64 is also partially received within an opening 68 in wedge member62 to maintain the pin in its supporting position between burst disk 44and support member 60.

In operation of the present exemplary embodiment, when initiator 36 isactivated, pin 64 will stroke or travel away from support member 60 andthrough opening 68 in wedge member 62 to release the wedge member 62from its supporting position. Pin 64 will then make contact with, andthereby rupture, burst disk 44, releasing the gas of first inflationchamber 32 through outlet opening 42. In an alternative exemplaryembodiment, pin 64 may be used solely for releasing wedge member 62, inwhich case the movement of the wedge member 62 from its supportingposition allows burst disk 44 to rupture.

During this activation event, wedge member 62 travels downwardly towardsa screen member 70. Screen member 70 is positioned to retain and/orprevent debris from exiting through an outlet conduit 72 of the housing38 (in particular, debris from wedge member 62 and portions of burstdisk 44). In the present exemplary embodiment, outlet conduit 72 isconfigured to provide fluid communication between first inflationchamber 32 and an inflatable cushion (not shown) after initiator 36 hasbeen activated and burst disk 44 has been removed from outlet opening42.

In the present exemplary embodiment, initiator 36 is angularlyconfigured such that a surface of support member 60 locates or supportswedge member 62 between the support member 60 and a portion of burstdisk 44 when the initiator 36 is in an un-activated state, as shown inFIG. 3. Furthermore, this arrangement allows wedge member 62 to supportburst disk 44 as it retains the pressurized gas within the firstinflation housing 32.

Wedge member 62 can further comprise another opening that is configuredto allow inflation gases to pass therethrough to allow for thecontrolled release of the inflator gas under extreme temperatures andpressures. It should, of course, be understood that wedge member 62 mayhave various configurations, and exemplary embodiments of the presentinvention are not limited to the specific configurations of wedge member62 as illustrated and described in accordance the present exemplaryembodiment.

In the present exemplary embodiment, as illustrated in FIG. 3, inflationhousing 34 is integrally formed and includes a notch 79 that extendsradially into the intersection of first and second inflation chambers32, 76. Second inflation chamber 76 comprises a substantially smallervolume for holding a second amount of inflation gas, which is to beprovided into first inflation chamber 32 and, ultimately, through outletopening 42 via an output orifice 81 disposed in divider plate 80, whichis secured to notch 79 to provide fluid communication between the firstinflation chamber 32 and second inflation chamber 76. Divider plate 80is formed with output orifice 81 extending longitudinally into secondinflation chamber 76 and an annularly shaped flange 83 extendinggenerally transversely to longitudinal axis 82.

In the present exemplary embodiment, divider plate 80 is joined to notch79 using DRW techniques, as illustrated in FIGS. 7-9, to form adeformation resistance weld joint 91. Inflation housing 34 has an insideand an outside surface 84, 85 and defines a longitudinal axis 82. Notch79 is shaped as a depression that extends radially inwardly withininflation housing 34 in a generally transverse direction to longitudinalaxis 82.

A lower surface 86 of annular flange 83 of divider plate 80 and an innersurface 87 of notch 79 proximate to second inflation chamber 76 definethe respective joining surfaces of weld joint 91. The depression ofnotch 79 extends in a direction generally parallel to the joiningsurfaces, both prior to and after resistance welding divider plate 80and notch 79 together.

With lower surface 86 of annular flange 83 and inner surface 87 of notch79 on the side of second inflation chamber 76 contacting one another, asdescribed above and depicted in FIGS. 7 and 8, weld joint 91 is formedby forcing notch 79 against annular flange 83 and welding them togetherto the point shown in FIG. 9. Notch 79 is compressed against annularflange 83 by engaging the notch 79 with a first electrode 88 andapplying pressure against the notch 79 with the first electrode 88 in afirst direction generally transverse to longitudinal axis 82, whilesimultaneously engaging divider plate 80 with a second electrode 89, andapplying pressure against the divider plate 80 with the second electrode89 in a generally longitudinal direction perpendicular to the firstdirection. Notch 79 and annular flange 83 are abutted against oneanother by applying sufficient pressure through first and secondelectrodes 88, 89, and moving at least one of the electrodes toward theother electrode, while resistance welding together the notch 79 and theannular flange 83.

The resistance welding is accomplished by applying an electrical currentbetween the electrodes for resistance heating of notch 79 and dividerplate 80 to a temperature at which a metallurgical bond is formed atbetween the respective joining surfaces 86, 87 and within the depressionof the notch. Pressure and electrical current can be maintained at alevel and for a period of time sufficient to substantially soften notch79 and annular flange 83 and force the softened material into theinterference juncture between the two parts. In this manner, thesoftened material can be forced to flow through a fairly long juncture,and the components to be joined can be maintained at an optimumtemperature for ensuring that a complete and high quality weld isformed. The depression of notch 79 can improve the quality or thecleanliness of weld joint 91 by preventing weld flash from reaching theinner diameter of the functioning area of the weld joint.

Further, in exemplary embodiments, it may be advantageous apply pressureand a first level of electrical current flow through notch 79 andannular flange 83 for a first period of time, for softening the annularflange 83 by electrical resistance heating and causing the softenedflange to deform against the notch 79, under the pressure exerted byfirst and second electrodes 88, 89, followed by the application of asecond level of electrical current, higher than the first level ofcurrent, for a second period of time sufficient to at least partiallymelt the annular flange 83, and form deformation resistance weld joint91 between the notch 79 and the flange 83.

By utilizing DRW techniques, the present exemplary embodiment makes itunnecessary to use two separate chambers when welding divider plate 80and thus requires just a single weld joint instead of multiple weldjoints. That is, inflation housing 34 can be integrally formed asdescribed above and shown in FIGS. 7-9, thereby reducing part costs andweight. It should further be appreciated that, for a joint of this type,the ability to deform the outer diameter of annular flange 83 withinnotch 79 using DRW techniques eliminates the close tolerance machiningrequired in prior joining methods and considerably simplifies,facilitates, and decreases the cost of both construction and operationof the equipment used to make the joint. In the present exemplaryembodiments, stops for the electrodes may be precisely designed forprecise control of the finished part length to make the performance ofthe inflator more repeatable. In addition, the use of DRW techniques canprovide for a reduced cycle time, much improved weld strength anddurability, and a decreased the heat effect in the parent metals causedby weld heat by providing the ability to heat treat the components inthe weld strength.

In the exemplary embodiment illustrated in FIGS. 7-9, divider plate 80is formed with output orifice 81 extending longitudinally into secondinflation chamber 76 so that lower surface 86 of annular flange 83 andinner surface 87 of notch 79 on the side of the second inflation chamber76 contact one another at the outset of the welding process. Asillustrated in FIGS. 7 and 8, such an arrangement is provided for bylongitudinally extending second electrode 89 within second inflationchamber 76 while applying pressure against the notch 79 with firstelectrode 88 in a direction generally transverse to the second electrode89. The geometry of this exemplary embodiment can provide for bettermechanical strength of divider plate 80 in withstanding burst pressureduring initiation. In an alternative exemplary embodiment, divider plate80 can be formed with output orifice 81 extending longitudinally intofirst inflation chamber 32 so that an upper surface 93 of annular flange83 and inner surface 87 of notch 79 proximate to the first inflationchamber 32 contact one another at the outset of the welding process, asillustrated in FIG. 10. This alternative geometry provides for improvedcontact between second electrode 89 and divider plate 80 for improvedelectrode life in manufacturing, and can be provided for bylongitudinally extending second electrode 89 within first inflationchamber 32 while applying pressure against the notch with firstelectrode 88 in a direction generally transverse to the second electrode89.

Referring once again to FIG. 3, exemplary inflator 30 also includes anend plate 90 disposed at an end of inflation housing 34 opposed toclosure assembly 78. End plate 90 is configured with a fill passageway92 and a sealing means 94 secured therein after a predetermined volumeof inflation gas is supplied to first and second inflation chambers 32,76. In exemplary embodiments, fill passageway 92 may be either closed orplugged in any fashion that allows first inflation chamber 32 to befilled with a first compressed volume of inflation gas and sealed. Innon-limiting exemplary embodiments, the gas stored in first and secondinflation chambers 32, 76 can comprise argon, helium, carbon dioxide,nitrogen, or equivalents or mixtures thereof.

In exemplary embodiments, initiator 36 can be electrically coupled to asensing and diagnostic module (not shown) that is configured to receiveand interpret signals from a plurality of vehicle sensors to determinewhether an activation signal is to be sent to the initiator. Inaccordance with the present exemplary embodiment, initiator 36 isreceived within an initiator retainer 96 that may comprise a portion ofclosure housing 38. Initiator retainer 96 helps position initiator 36 sothat, upon receipt of such an activation signal, initiator 36 will fire,causing pin 64 to stroke and rupture burst disk 44. Wedge member 62 willthen be free to move, thereby allowing the gas from first and secondinflation chambers 32, 76 to pass through outlet conduit 72.

As illustrated in FIG. 3, outlet opening 42 is substantially larger thanoutput orifice 81 in the present exemplary embodiment. As a result, theinflation output from second inflation chamber 76 is at a substantiallylower flow rate for an extended period of time. This time period issubstantially longer than the period of time for the inflation gases toflow out of first inflation chamber 32. Therefore, in accordance withthe present exemplary embodiment, first inflation chamber 32 is used toprovide an initial output for initially deploying and inflating theinflatable cushion 10, while second inflation chamber 76 is used toprovide a secondary or supplemental inflation output during and afterthe initial inflation of the inflatable cushion 10. The output of secondinflation chamber 76 is configured to counteract the leakage of theinflation gases from the inflatable cushion 10 during initial deploymentperiod. In other words, to provide an extended period of inflation ofthe inflatable cushion 10, first inflation chamber 32 is used to providean initial inflation output to deploy the inflatable cushion 10 into adesired inflated configuration, and thereafter any leakage of theinflation gases used to inflate the inflatable cushion 10 arecounteracted by the supplemental inflation output of second inflationchamber 76 as smaller output orifice 81 allows the supplementalinflation to be provided over a longer time period than is typical forrelease of all the gases in a single stage inflator.

During operation of inflator 30 of the present exemplary embodiment, theexternal support member 60 for metal membrane or burst disk 44 beginspositioned at an angle to initiator 36, as described above. Upon beingactivated, initiator 36 pressurizes a chamber behind the pin that causesto the pin to stroke and release wedge member 62. Thereafter, thepressure load on burst disk 44 creates a resultant force on wedge member62 that pushes the wedge member to the side away from the burst disk.Burst disk 44 then ruptures, allowing gas to exit, and screen member 70captures wedge member 62.

Referring now to FIG. 11, an alternative exemplary embodiment of aninflator manufactured in accordance with the present invention is shown.In exemplary inflator 130, component parts performing similar oranalogous functions to those in the exemplary embodiment described withregard to FIG. 3 above are labeled in multiples of 100.

In the present exemplary embodiment, a metal membrane or burst disk 144and a wedge member 162 of a closure assembly 178 are located on a centeraxis of inflator 130. Wedge member 162 is attached directly to burstdisk 144 and also contacts a narrow tip 161 of an initiator support cap160 off-center on a parallel axis. In this embodiment, support cap 160is located over initiator 136. During activation of initiator 136, achamber 159 behind support cap 160 is pressurized, causing the supportcap 160 to stroke and contact wedge member 162, thereby imparting axialand radial forces on the wedge member 162. The component forces ofsupport cap 160 operate to move wedge member 162 so that burst disk 144is unsupported and accordingly ruptures to allow the gas to exit.Thereafter, a screen member 170 captures burst disk 144. In exemplaryembodiments, wedge member 162 may be fixedly secured to burst disk 144or merely supported on the burst disk by support cap 160.

In accordance with the present exemplary embodiment, closure housing 138is joined to outlet plate 140 using DRW techniques in the same manner asthe analogous parts of the exemplary embodiment of FIG. 3. Additionally,divider plate 180 is joined to notch 179 using DRW techniques in thesame manner as the analogous parts of the exemplary embodiment of FIG.3. Exemplary embodiments of these methods are described above andillustrated in FIGS. 4-10.

In the present exemplary embodiment, support cap 160 and wedge member162 are disposed between burst disk 144 and initiator 136. Support cap160 defines chamber 159 to be in fluid communication with initiator 136.Wedge member 162, which is located adjacent to and wedged between burstdisk 144 and support cap 160, has an outer periphery or diameter that isless than the outer periphery or diameter of the burst disk 144. Asillustrated in FIG. 11, tip 161 of support cap 160 is disposed off axis,but parallel, to a tip 163 of wedge member 162. Of course, otherconfigurations (such as, for example, non-parallel tips 161, 163) arecontemplated in alternative exemplary embodiments.

During operation of the present exemplary embodiment, when initiator 136is activated, the pressure in chamber 159 behind support cap 160increases to cause the support cap 160 to stroke away from the initiator136. This causes tip 161 of support cap 160 to act on tip 163 todislodge wedge member 162, thereby causing the wedge member to travelaway from burst disk 144. Thereafter, burst disk 144, no longersupported by wedge member 162, will be allowed to rupture so that thegas of first inflation chamber 132 releases through outlet opening 156.

While the invention has thus far been described above with reference tospecific exemplary embodiments of a side airbag inflator comprising afirst chamber 32, 132 and a second chamber 76, 176 that arelongitudinally aligned, the broader practice of the invention is notnecessarily so limited. As such, the present invention is not intendedto be limited to the specific exemplary embodiments and configurationsillustrated in the Figures and described herein, as they are consideredancillary to the present invention.

Moreover, exemplary embodiments of inflators in accordance with thepresent invention are contemplated for use with numerous other airbagmodules. For instance, in addition to side airbag modules, the inflatormay be configured as a component of a driver side airbag module or apassenger side airbag module.

Reference will now be made to FIG. 12, in which the interior of anexemplary vehicle 210 for transporting an operator 212 and a passenger214 is illustrated. Vehicle 210 may include a driver side airbag module220 mounted within the steering wheel 218 for protection of vehicleoperator 212. Vehicle 210 can also include a passenger side airbagmodule 216 mounted within the dash panel in substantially opposingrelation to vehicle passenger 214. Activation of airbag modules 216, 220typically takes place upon the occurrence and measurement ofpredetermined vehicle conditions such as deceleration at a rateexceeding a predetermined value.

Referring now to FIG. 13, an exemplary embodiment of an assembly fordriver side airbag module 220 is illustrated. Airbag module 220 issuitably mounted to a central hub or armature of a steering wheel 218.Typically, some form of mounting mechanism will be provided to mount theairbag module assembly 220 components to each other and to the steeringwheel 218.

Airbag module 220 includes a cover plate 222, an inflatable airbagcushion 224, an annular cushion ring 226, an annular cover retainer 228,an inflator 230, and an annular retaining plate or pad retainer plate232. Typically, cushion ring 226 is formed from metal and secured to oneside of an inflator opening of airbag cushion 224, while cover retainer228, which is also formed from metal, is disposed on the other side ofthe inflator opening. Thus, a periphery of the inflator opening ofairbag cushion 224 is disposed between cushion ring 226 and coverretainer 228, and the two are drawn together by tightening of aplurality of nuts 238 about a plurality of threaded bolts 234 passingthrough openings in the cushion ring 226, the periphery of the inflationopening of the inflatable cushion 224, and the cover retainer 228. Inother exemplary configurations, cushion ring 226 can be secured to coverretainer 228 by a plurality of bolts 234 passing through openings in thecushion ring, the cover retainer 228, and retaining plate 232.Thereafter, plurality of nuts 238 are disposed about threaded bolts 234to secure the assembly together.

Cushion ring 226 is typically used for mounting/attaching airbag cushion224 to the airbag module. In other words, cushion ring 226 secures theopening of airbag cushion 224 about a portion of inflator 230 as well asretaining plate 232, which is fixedly secured to the vehicle 210. Inexemplary airbag module assemblies, cushion ring 226 can be a separatemetal component that is riveted or bolted together with other adjoiningcomponents in the airbag module 220, such as cover plate 222, so as tomerely pinch/squeeze the airbag cushion 224 between the adjoiningcomponents. Cover plate 222 is used to secure the airbag module's cover(not shown) in the final assembly.

As illustrated in FIG. 13, airbag module 220 includes an inflator 230manufactured in accordance with an exemplary embodiment of the presentinvention. Inflator 230 is configured to generate inflator gas upon thesensing of predetermined vehicle conditions (for example, rapiddeceleration) to inflate airbag cushion 224. In exemplary embodiments,inflator 230 can be of any conventional construction for generatinginflator gas to inflate the airbag cushion 224, such as a single stageinflator. Inflator 230 has a generally cylindrical housing portion 242secured to a generally circular base plate 236 that suitably engageswith cover retainer 228 and cushion ring 226. A plurality of vent ports240 are formed in and extend around housing 242 into inflator 230 in aradial manner. Base plate 236 also includes an opening 244 to permit aninitiator to extend into inflator 230. It should be understood that thenumber and dimension of vent ports 240 may be varied according to theprecise application and configuration of inflator 230 in particularexemplary embodiments.

In exemplary embodiments of the present invention, housing portion 242and base plate 236 of inflator 230 are secured to one another using DRWtechniques, as illustrated in FIGS. 12 and 13, to form deformationresistance weld joint 278. Housing 242 defines a longitudinal axis 246and an inside and an outside surface 248, 250 of inflator 230. Baseplate 236 extends across a lower end 252 of housing 242 in a generallytransverse direction to longitudinal axis 246.

To define the joining surfaces of weld joint 278, lower end 252 ofhousing 242 is formed with two angled chamfers 258, 260 on inside andoutside surfaces 248, 250 respectively, and an upper surface 254 of baseplate 236 is formed with an annular groove 262 that is generallyconcentric with and of a similar diameter to the lower end 252 of thehousing. This configuration of the joining surfaces is intended toproduce two concentric deformation resistance weld interfaces 279, 280at the angled chamfers 258, 260 that are welded at the same time, asdescribed below.

As best seen in FIG. 14, at the outset of the welding process, lower end252 of housing 242 is circumferentially aligned with annular groove 262of base plate 236. The transverse width of housing 242, however, isgreater than the transverse width of annular groove 262 at the outset ofthe welding process. This differential provides for diametricalinterference in the mating parts to permit deformation and sliding ofthe mating surfaces along each other during the weld process.

When lower end 252 of housing 242 is longitudinally aligned with annulargroove 262 of base plate 236, a weld joint 278 can be formed betweenhousing portion 242 and base plate 236. In the present exemplaryembodiment, the welded joint 278 is formed by sliding lower end 252 ofhousing 242 into annular groove 262 while forcing the two componentsagainst each other under sufficient pressure to form an interferencefit. As shown in FIG. 15, the welding process is complete at a point atwhich lower end 252 of housing 242 engages the transverse section ofannular groove 262.

To perform the welding process described above, lower end 252 of housing242 is compressed into annular groove 262 by engaging the housing with afirst electrode 264, and applying pressure against the housing with thefirst electrode 264 in a first direction generally perpendicular to theannular housing 242 of inflator 230, while simultaneously engaging baseplate 236 with a second electrode 266, and applying pressure against theoutlet plate with the second electrode 266 in a direction perpendicularthe first direction. In the present exemplary embodiment, secondelectrode 266 includes a direct water-cooling mechanism 272 to providefor less heat effect in the area of base plate 236 that is not part ofweld joint 278. Second electrode 266 also comprises a clearance aperture268 to receive an initiator 270 where the initiator 270 has beenreceived in opening 244 of base plate 236 prior to welding, asillustrated in FIG. 15. In alternative exemplary embodiments, initiator270 need not be installed in opening 244 until after welding.

The interference fit is formed by applying sufficient pressure throughfirst and second electrodes 264, 266 and moving at least one of theelectrodes toward the other electrode, while resistance welding togetherlower end 252 of housing 242 and annular groove 262 by applying anelectrical current between the electrodes for resistance heating thehousing and the outlet plate to a temperature at which a metallurgicalbond is formed between the joining surfaces. Pressure and electricalcurrent can be maintained at a level and for a period of time sufficientto substantially soften housing 242 and base plate 236 and force thesoftened material into the interference juncture between the two parts.In this manner, the softened material can be forced to flow through afairly long juncture, and the components to be joined can be maintainedat an optimum temperature for ensuring that a complete and high qualityweld is formed.

Further, in exemplary embodiments, it may be advantageous apply pressureand a first level of electrical current flow through housing 242 andbase plate 236 for a first period of time, for softening the housing byelectrical resistance heating and causing the softened housing to deformagainst the base plate, under the pressure exerted by first and secondelectrodes 264, 266, followed by the application of a second level ofelectrical current, higher than the first level of current, for a secondperiod of time sufficient to at least partially melt the housing, andform deformation resistance weld joint 278 between the housing and thebase plate.

It should be appreciated that for a joint of this type, the ability toslide lower end 252 of housing 242 into annular groove 262 using DRWtechniques eliminates the close tolerance machining required in priorjoining methods, simplifies the form with which the annular groove canbe provided, and considerably simplifies, facilitates, and decreases thecost of both construction and operation of the equipment used to makethe joint. For instance, as illustrated in FIG. 15, the weldingmechanism can be provided with an insulation plate 274 disposed adjacentto an upper surface 276 of inflator 230 to control the proximity of baseplate 236 to first electrode 264 during welding. Alternatively, stopsfor the electrodes 264 and 266 may be precisely designed to provide formore precise control of the finished part length and thereby make theperformance of the inflator more repeatable. Moreover, in alternativeexemplary embodiments, annular groove 262 of base plate 236 may insteadbe provided as an interstitial annular groove that extends to theperiphery of upper surface 254 of the base plate, as illustrated in FIG.16, so that only a single deformation resistance weld interface 281 isformed between a single angled chamfer 258 on inside surface 248 ofhousing 242 and upper surface 254 of the base plate 236. Thisconfiguration can provide for weld joints of a single-sided geometrythat may be adequately strong for the intended service, while permittingfor improved contact between the electrodes 264 and 266 and outsidesurfaces of the mating components. In other alternative exemplaryembodiments, angled chamfers 258, 260 and/or annular groove 262 havingunequal geometries so that two unequal, concentric weld interfaces. Inaddition, the use of DRW techniques can provide for a reduced cycletime, much improved weld strength and durability, and a decreased theheat effect in the parent metals caused by weld heat by providing theability to heat treat the components in the weld strength.

Referring back to FIG. 13, in response to a sudden deceleration of thevehicle, a controller such as a sensing and actuating system (not shown)provides an ignition signal to the initiator to initiate deploymentinflation of the airbag cushion 224. Upon actuation of the initiator inresponse to the ignition signal, inflator 230 discharges an appropriatevolume of gas from vent ports 240 into airbag cushion 224.

Exemplary inflator 230 is described above and illustrated in FIG. 13 asa component of a driver side airbag module for installation in a driverside of a vehicle to protect the driver thereof. It should berecognized, however, that inflator 230 can be a component of otherpassive restraints in alternative exemplary embodiments. For instance,inflator 230 can be a component of a passenger side airbag module thatcan be mounted within a vehicle's dash panel in exemplary embodiments,such as airbag module 216 shown in FIG. 12, for protection of anoccupant in the vehicle's passenger seat.

It should be recognized that the present invention is not intended to belimited to the specific configurations provided in the exemplaryembodiments described above and illustrated in the drawings, as they areconsidered ancillary to the present invention. That is, the scope of thepresent invention encompasses many other vehicle configurations andinflator arrangements in alternative embodiments. For example, thevehicle may include three rows of seats such as, but not limited to,sports utility vehicles, station wagons, and vans or minivans.Alternatively, the vehicle may comprise only a single row of seats suchas, but not limited to, sports coups. Therefore, exemplary embodimentsof an airbag inflator in accordance with the present invention may beeasily modified to accommodate all types of vehicles and airbag moduleassemblies in several different types of configurations.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. An inflator for inflating an inflatable cushion of an airbag module,the inflator comprising: an outer housing; a divider plate securedwithin the outer housing to define a first chamber and a second chamberof the outer housing, the divider plate having an orifice disposedtherein, the orifice providing fluid communication between the firstchamber and the second chamber, the divider plate being joined to theouter housing by a deformation resistance weld, the deformationresistance weld being formed by contacting the outer housing with afirst electrode at an exterior portion of the outer housing proximate tothe divider plate, contacting the divider plate with a second electrodedisposed within the outer housing, and applying a voltage through thefirst and second electrodes to adhere a portion of the outer housing toa portion of the divider plate; and a closure assembly configured toseal the first chamber at a first end of the outer housing, the closureassembly having a closure housing and an outlet plate disposed withinthe closure housing, the outlet plate having an outlet openingconfigured to receive a burst disk, the outlet plate being joined to theclosure housing by contacting the outlet plate with a third electrodedisposed about the outlet plate, contacting an exterior portion of theclosure housing with a fourth electrode, and forming a deformationresistance weld between the closure housing and the outlet plate,wherein the outer housing is joined to the outlet plate remote from theclosure housing at the first end of the outer housing, and wherein thefirst chamber has a first volume of compressed inflation gas and thesecond chamber has a second volume of compressed inflation gas, thesecond volume being smaller than the first volume, the second chamberbeing configured to route compressed inflation gas therein to the firstchamber through the orifice of the divider plate.
 2. The inflator ofclaim 1, wherein the divider plate is remotely disposed from both afirst end and a second end of the outer housing, wherein the firstchamber is defined by a first annular wall section of the outer housingand the divider plate, the second chamber is defined by a second annularwall section of the outer housing and the divider plate, and the firstand second annular wall sections are integrally formed and adjoined at anotch section of the outer housing proximate to the divider plate, andwherein the notch section is formed as a radial depression extendinginto the outer housing.
 3. The inflator of claim 2, wherein the dividerplate is formed with a centrally protruding portion extendinglongitudinally into the second chamber from an annular flange that issecured to the notch section of the outer housing by the deformationresistance weld, and wherein a surface of the annular flange of thedivider plate that generally faces the first chamber and an innersurface of the notch section that generally faces the second chamberdefine respective joining surfaces that are abutted against one anotherwhen the deformation resistance weld is formed.
 4. The inflator of claim2, wherein the divider plate is formed with a centrally protrudingportion extending longitudinally into the second chamber from an annularflange that is secured to the notch section of the outer housing by thedeformation resistance weld, wherein a surface of the annular flange ofdivider plate that generally faces the first chamber and an innersurface of the notch section that generally faces the second chamberdefine respective joining surfaces that are abutted against one anotherwhen the deformation resistance weld is formed, and wherein the secondelectrode has an opening configured to receive the centrally protrudingportion of the dividing plate therein and is disposed within the firstchamber of the outer housing when the divider plate is joined to theouter housing.
 5. The inflation device of claim 1, wherein the dividerplate is positioned in a desired location relative to the outer housingutilizing at least one of the first and second electrodes when thedeformation resistance weld is formed.
 6. The inflator of claim 1,further comprising an end plate joined to the second chamber at a secondend of the outer housing, the end plate being configured with a fillpassageway for allowing inflation gas to pass into the second chamber.7. The inflator of claim 6, wherein the closure housing is in fluidcommunication with the inflatable cushion in a side airbag module, andwherein the closure housing is configured to supply inflation gas to theinflatable cushion.
 8. An inflator for inflating an inflatable cushionof an airbag module, the inflator comprising: an outer housing; adivider plate secured within the outer housing to define a first chamberand a second chamber of the outer housing, the divider plate having anorifice disposed therein, the orifice providing fluid communicationbetween the first chamber and the second chamber, the divider platebeing joined to the outer housing by a weldment disposed between theouter housing and the divider plate; and a closure assembly configuredto seal the first chamber at a first end of the outer housing, theclosure assembly having a closure housing and an outlet plate disposedwithin the closure housing, the outlet plate having an outlet openingconfigured to receive a burst disk, the outlet plate being joined to theclosure housing by a second weldment disposed between the closurehousing and the outlet plate, wherein the outer housing is joined to theoutlet plate remote from the closure housing at the first end of theouter housing, and wherein the first chamber has a first volume ofcompressed inflation gas and the second chamber has a second volume ofcompressed inflation gas, the second volume being smaller than the firstvolume, the second chamber being configured to route compressedinflation gas therein to the first chamber through the orifice of thedivider plate.